Nanodiamonds are ultrafine diamond particles having a very large specific surface area, and have a high mechanical strength and electric insulation, and an excellent thermoconductivity. The nanodiamonds also have a deodorant effect, an antibacterial effect and a chemical resistance. Hence, the nanodiamonds are used as an abrasive material, an electroconductivity-imparting material, an insulating material, a deodorant, an antibacterial and the like.
Nanodiamonds are usually synthesized by a detonation method. The nanodiamonds obtained by the detonation method forms agglutinates in many cases; the agglutinate is subjected to a deagglutinating treatment using a crusher such as a bead mill to thereby obtain so-called one-digit nanodiamonds having a particle diameter D50 (median diameter) of less than 10 nm (Patent Literatures 1, 2).